Journal of Marine Science and Engineering

18 pages, 13069 KiB

Open AccessArticle

Horizontal-Transverse Coherence of Bottom-Received Acoustic Field in Deep Water with an Incomplete Sound Channel

by Qianyu Wang, Zhaohui Peng, Bo Zhang, Feilong Zhu, Wenyu Luo, Tongchen Wang, Lingshan Zhang and Junjie Mao

J. Mar. Sci. Eng. 2024, 12(12), 2354; https://doi.org/10.3390/jmse12122354 (registering DOI) - 21 Dec 2024

Abstract

The horizontal-transverse coherence of low-frequency (300 Hz) and long-range (10–40 km) acoustic fields near the bottom in deep water is investigated based on experimental data obtained from the South China Sea. The results indicate that the horizontal-transverse coherence length exhibits a strong dependence [...] Read more.

The horizontal-transverse coherence of low-frequency (300 Hz) and long-range (10–40 km) acoustic fields near the bottom in deep water is investigated based on experimental data obtained from the South China Sea. The results indicate that the horizontal-transverse coherence length exhibits a strong dependence on the source-receiver distance, with fluctuations consistent with sound intensity trends. In high-intensity regions, the horizontal-transverse coherence is relatively high, with a coherence length exceeding 600 λ, where λ is the acoustic wavelength, whereas in low-intensity regions, the horizontal-transverse coherence decreases significantly, with the coherence length shortening to 10–30 λ. The physical mechanisms underlying the horizontal-transverse coherence are analyzed using the ray theory. In high-intensity regions, the energy of the dominant ray (the ray with the highest energy) accounts for over 70% of the total energy of the rays, exerting a decisive influence on the coherence coefficient and leading to stable horizontal-transverse coherence in the received acoustic field. In contrast, in low-intensity regions, the energy distribution is dispersed, and when amplitude and phase disturbances due to spatial inhomogeneity are introduced, the horizontal coherence deteriorates significantly. The numerical simulations are also performed, and the results are consistent with the experimental observations. Full article

(This article belongs to the Section Ocean Engineering)

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17 pages, 5298 KiB

Open AccessArticle

Stratification Effects on Estuarine Mixing: Comparative Analysis of the Danshui Estuary and a Thermal Discharge Outlet

by Yaozhao Zhong and Hwa Chien

J. Mar. Sci. Eng. 2024, 12(12), 2353; https://doi.org/10.3390/jmse12122353 (registering DOI) - 21 Dec 2024

Abstract

Estuaries serve as transitional zones between rivers and the ocean, and their mixed dynamic characteristics are crucial for the transport, transformation, and cycling of materials. This study investigates the mixing characteristics and their dominant factors in the Danshui Estuary and thermal discharge outlets [...] Read more.

Estuaries serve as transitional zones between rivers and the ocean, and their mixed dynamic characteristics are crucial for the transport, transformation, and cycling of materials. This study investigates the mixing characteristics and their dominant factors in the Danshui Estuary and thermal discharge outlets through field measurements. Based on CTD (Conductance Temperature Depth) profiles and nutrient concentration measurements, the Danshui Estuary exhibited significant stratification during the October 2016 cruise, while vertical mixing was uniform during the March 2017 cruise. Vertical mixing was suppressed during stratification, but the nutrient concentration varied with salinity in a manner that was similar to non-stratified conditions, generally conforming to the theoretical dilution curve, which means physical mixing dominated here, indicating that horizontal mixing is predominant in the Danshui Estuary. The spatial scale calibrated horizontal dispersion coefficients were measured as 9.16 ± 1.57 m² s⁻¹ and 11.84 ± 1.71 m² s⁻¹ for stratified and non-stratified conditions, respectively, highlighting the Danshui Estuary’s strong horizontal mixing. Thermal discharge outlets are an important type of estuarine environment in non-natural estuaries. The 3D thermohaline structure measured by the underway CTD revealed an upwelling of cold and high-salinity water during the flood tide. The calculated Richardson number during the flood tide was approximately 0.7, indicating a very strong stratification effect. The horizontal dispersion coefficients calibrated by spatial scale showed no significant difference between different tides (flood tide: 0.53 ± 0.18 m² s⁻¹, ebb tide: 0.46 ± 0.17 m² s⁻¹). Therefore, the slower temperature decay during the flood tide, as reflected by the e-folding time (flood tide: 4.19 ± 2.33 min, ebb tide: 2.14 ± 0.40 min), is attributed to the strong stratification. Based on these findings, it is recommended that the power plant mitigates the impact of waste heat on the marine environment by increasing discharge during the ebb tide and reducing it during the flood tide. Full article

(This article belongs to the Section Physical Oceanography)

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17 pages, 8063 KiB

Open AccessArticle

Research on the Comparison of the Flow Evolution Mechanisms of a Water-Jet Pump Between Valley and Peak Conditions

by Min Liu, Yun Long, Yingying Zheng, Jinqing Zhong and Hong Yin

J. Mar. Sci. Eng. 2024, 12(12), 2352; https://doi.org/10.3390/jmse12122352 (registering DOI) - 21 Dec 2024

Abstract

The pump hump significantly influences the vibration and operational stability of pumps. During the development of the mixed-flow waterjet pump, our team found that the pump performance curve had a hump phenomenon and the platform had vibration, so it was suspected that there [...] Read more.

The pump hump significantly influences the vibration and operational stability of pumps. During the development of the mixed-flow waterjet pump, our team found that the pump performance curve had a hump phenomenon and the platform had vibration, so it was suspected that there was a strong secondary flow in the hump region. The calculation model is the SST k-ω turbulence model. The impeller and diffuser use structured grids. By using high-speed photography technology, we map the cavitation flow structures, thereby demonstrating the evolution of cavitation processes. The hump curve was obtained by an experimental test. By comparing the test data and numerical simulation, the consistency of the method and the hump curve is verified. A comparative analysis is performed to investigate the variations in the distribution of internal vortex structures and the evolution of rotating stalls in the impeller. In the valley condition, the main frequency of pressure pulsation in the inlet section of the impeller is 0.75 times the shaft frequency, the main frequency in the middle and outlet sections of the impeller is 1 times the shaft frequency, and the main frequency in the diffuser basin is 1.5 times the shaft frequency, the main frequency in the peak condition at the points of Span = 0.1 and Span = 0.5 of the impeller is the diffuser frequency, the main frequency at the point of Span = 0.9 is the impeller blade frequency, and the main frequency in the diffuser basin is either the shaft frequency or the diffuser blade frequency. This research reveals the characteristics of vortex flow in the pump under hump conditions. It reveals that the evolution mechanism of the hump offers a guide value for the subsequent hydrodynamic design of the hump. Full article

(This article belongs to the Section Ocean Engineering)

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23 pages, 15475 KiB

Open AccessArticle

Hydrodynamic Performance and Mooring Safety Assessment of an Offshore Floating Movable Fish Cage

by Sung-Jae Kim, Seong-Jae Jeong and Sung-Ju Park

J. Mar. Sci. Eng. 2024, 12(12), 2351; https://doi.org/10.3390/jmse12122351 (registering DOI) - 21 Dec 2024

Abstract

This study evaluates the hydrodynamic performance of a movable fish cage equipped with a spread mooring system in offshore condition. It investigates the global behavior and safety of a mooring system under environmental influences such as waves, currents, and biofouling. A numerical model [...] Read more.

This study evaluates the hydrodynamic performance of a movable fish cage equipped with a spread mooring system in offshore condition. It investigates the global behavior and safety of a mooring system under environmental influences such as waves, currents, and biofouling. A numerical model was developed using the Cummins equation and a lumped-mass line model to capture the coupling effects between the floating structure and mooring lines. The steel frame was modeled using Morison members, whereas fishing nets were represented by a screen model incorporating drag forces. Parametric studies were performed to assess the effects of varying mooring line lengths, current speeds, and biofouling on cage behavior. Evidently, heavier chains reduced excursions but increased tension, whereas high current speeds increased the line tension (owing to increased drift) and mooring line stiffness by up to 66%. Biofouling increased the maximum excursion by 6% and line tension by up to 17%. Safety evaluations based on the American Bureau of Shipping rules examined intact and damaged conditions, comparing estimated line tensions with allowable values. The findings confirm that the mooring system ensures reliable station-keeping performance even under challenging conditions, validating its suitability for offshore deployment and ensuring the safety and stability of floating fish cage systems. Full article

(This article belongs to the Special Issue Numerical Analysis and Modeling of Floating Structures)

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30 pages, 1986 KiB

Open AccessArticle

Consensus-Based Formation Control and Gyroscopic Obstacle Avoidance for Multiple Autonomous Underwater Vehicles on SE(3)

by Qingzhe Zhen, Lei Wan, Yuansheng Zhang and Dapeng Jiang

J. Mar. Sci. Eng. 2024, 12(12), 2350; https://doi.org/10.3390/jmse12122350 (registering DOI) - 21 Dec 2024

Abstract

To address the control challenges posed by increasingly complex mission scenarios, this paper aims to develop an advanced formation control and obstacle avoidance strategy for autonomous underwater vehicles (AUVs) in SE(3). This study establishes a dynamic model for fully actuated AUVs and designs [...] Read more.

To address the control challenges posed by increasingly complex mission scenarios, this paper aims to develop an advanced formation control and obstacle avoidance strategy for autonomous underwater vehicles (AUVs) in SE(3). This study establishes a dynamic model for fully actuated AUVs and designs a consensus-based formation control strategy to achieve coordinated movement. Motivated by limitations of existing obstacle avoidance strategies such as local minima issues and mutual interference between formation members in high-density environments, this paper introduces a novel gyroscopic force-based obstacle avoidance method. The proposed approach leverages the principles of rotation and angular momentum conservation to enable effective obstacle avoidance while maintaining formation integrity. Simulation results demonstrate the effectiveness of the proposed methodology in achieving robust formation control and collision avoidance under challenging conditions. Full article

(This article belongs to the Section Ocean Engineering)

16 pages, 10055 KiB

Open AccessArticle

Coastal Protection for Tsunamis

by Angela Santos and Nelson Mileu

J. Mar. Sci. Eng. 2024, 12(12), 2349; https://doi.org/10.3390/jmse12122349 (registering DOI) - 21 Dec 2024

Abstract

Previous research showed that a tsunami similar to the 1755 event would inundate Caxias’ low-ground areas in Oeiras municipality, Portugal. However, the streets of downtown Caxias were not well reproduced, which is a limitation of the area’s mitigation strategies and evacuation plan. For [...] Read more.

Previous research showed that a tsunami similar to the 1755 event would inundate Caxias’ low-ground areas in Oeiras municipality, Portugal. However, the streets of downtown Caxias were not well reproduced, which is a limitation of the area’s mitigation strategies and evacuation plan. For these reasons, new Lidar data were used for the first time in Portugal. The new local topography data allowed the construction of a more accurate DEM, which was used in the tsunami numerical model to update and improve the inundation results. As a complement, a field survey was conducted in several locations to assess coastal features and protection. The numerical model results show that low-ground areas up to 6 m in height were inundated by the tsunami, including the residential area, the road, and the railway. To stop the tsunami waves from inundating these areas, it is proposed that the construction of more sea walls up to 7 m in height and a third bridge over the Barcarena Stream, only for pedestrians, ranging from 5 to 7 m in height, which will serve as a gate for the incoming tsunami waves. These coastal protections should be part of the strategy to mitigate coastal overtopping (winter storm surges and tsunamis) not only in Caxias but also in other coastal zones. Full article

(This article belongs to the Special Issue Coastal Disaster Assessment and Response)

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20 pages, 1100 KiB

Open AccessArticle

Research on Fault Diagnosis Method for Marine Diesel Engines Based on Multi-Scale Attention Mechanism Transformer

by Manyi Chen, Huibing Gan and Hangjie Wu

J. Mar. Sci. Eng. 2024, 12(12), 2348; https://doi.org/10.3390/jmse12122348 (registering DOI) - 21 Dec 2024

Abstract

In modern intelligent shipping, ensuring the stable and reliable technical condition of marine diesel engines is critical for safe and efficient vessel operations. Conventional fault diagnosis approaches and many existing Transformer-based methods often focus on single-scale features, potentially overlooking subtle fault indicators and [...] Read more.

In modern intelligent shipping, ensuring the stable and reliable technical condition of marine diesel engines is critical for safe and efficient vessel operations. Conventional fault diagnosis approaches and many existing Transformer-based methods often focus on single-scale features, potentially overlooking subtle fault indicators and reducing diagnostic accuracy under complex working conditions. To address these limitations, this paper proposes a Multi-Scale Attention Transformer (MSAT) model that integrates both high- and low-resolution attention mechanisms. This multi-scale strategy enhances the extraction of detailed and coarse-grained features, improving the model’s capacity to detect and characterize complex diesel engine faults. Additionally, an optimized Nadam optimizer is employed to refine convergence speed and accuracy, surpassing the Adam-based baseline by 0.71%. Rigorous testing on a publicly available diesel engine fault dataset demonstrates that the MSAT model achieves a diagnostic accuracy of 99.86% at a 60 dB signal-to-noise ratio (SNR), outperforming established models such as GRU and LSTM by more than 1%. Even under severe noise interference (0 dB SNR), the model maintains a high accuracy of 96.86%, highlighting its robustness and suitability for real-time monitoring in challenging marine environments. By quantitatively validating these improvements in diagnostic accuracy and noise resistance, this work offers a novel and effective solution for predictive maintenance and operational condition assessment of marine diesel engines, contributing to the reliability and safety of intelligent shipping systems. Full article

(This article belongs to the Section Ocean Engineering)

16 pages, 5883 KiB

Open AccessArticle

A Vessel Position Precision Analysis Based on a Two-Star Combined Approach

by Yulin Wu, Chao Zhuo, Tao He, Gangjun Liu and Qingqing Liu

J. Mar. Sci. Eng. 2024, 12(12), 2347; https://doi.org/10.3390/jmse12122347 (registering DOI) - 21 Dec 2024

Abstract

Traditional celestial navigation mainly utilized the sextant to measure the attitude and the position contour method to calculate and resolve the vessel’s positioning problem, but these methods are not rigorous, having major deficiencies in the positioning accuracy. Currently, the small field-of-view star sensor [...] Read more.

Traditional celestial navigation mainly utilized the sextant to measure the attitude and the position contour method to calculate and resolve the vessel’s positioning problem, but these methods are not rigorous, having major deficiencies in the positioning accuracy. Currently, the small field-of-view star sensor is becoming the main attitude measurement equipment on vessels, and its measurement accuracy directly affects the vessel positioning results. Aiming at this problem, this research provides a model of small field-of-view star sensor positioning accuracy based on the two-star combination method, and numerical solutions are given. In addition, it focuses on the influence of the measurement error of the star sensor, especially the elevation angle error, on the positioning accuracy of the vessel and gives the star selection strategy for practical application. In particular, the star selection strategy is also applicable to other two-star positioning methods. The results show that the analytical solution is computationally simple and real-time, and the effect of measurement errors on positioning can be minimized by the star selection strategy. This study reveals the error influence mechanism based on the dual-star combination approach, which has significant implications for practical vessel navigation using small-field-of-view star sensors. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 8538 KiB

Open AccessArticle

An Integrative Approach to Assess and Map Zostera noltei Meadows Along the Romanian Black Sea Coast

by Oana Alina Marin, Florin Timofte, Adrian Filimon, Alina Mihaela Croitoru, Wouter van Broekhoven, Charlotte Harper and Roosmarijn van Zummeren

J. Mar. Sci. Eng. 2024, 12(12), 2346; https://doi.org/10.3390/jmse12122346 (registering DOI) - 20 Dec 2024

Abstract

Seagrass meadows, including those formed by Zostera noltei, play a crucial role in marine ecosystem health by providing habitat stability and coastal protection. In the Romanian Black Sea, Z. noltei meadows are critically endangered due to pressures from eutrophication, habitat loss, and [...] Read more.

Seagrass meadows, including those formed by Zostera noltei, play a crucial role in marine ecosystem health by providing habitat stability and coastal protection. In the Romanian Black Sea, Z. noltei meadows are critically endangered due to pressures from eutrophication, habitat loss, and climate change. This study presents a comprehensive baseline assessment of Z. noltei meadows near Mangalia, Romania, utilizing in situ field methods and UAV mapping conducted in the spring and summer of 2023. Seven meadow sites (Z1–Z7) were identified, with notable variability in density, shoot counts, and coverage across sites. Site Z1 exhibited the highest density (1223 shoots/m⁻²) and Z5 and Z7 the longest leaves (an average of 60 cm), reflecting possible environmental influences. Statistical analyses revealed significant inter-site differences in shoot density and leaf length, with density emerging as a primary differentiator. Ex situ analyses of epiphyte load indicated a median, balanced epiphyte load. This baseline dataset supported the selection of Z1 as a reference donor site for seagrass relocation activities along the Romanian coast in 2023. By providing critical insights into Z. noltei structure and health, this study supports future conservation efforts and evidence-based management of these vulnerable coastal habitats. Full article

(This article belongs to the Section Marine Ecology)

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20 pages, 9360 KiB

Open AccessArticle

Distribution and Long-Term Variation of Wetland Land Cover Types in the Yellow River Delta Remote Sensing Monitoring

by Chao Zhou, Qian Zhao, Tong Wu, Xulong Liu and Yanlong Chen

J. Mar. Sci. Eng. 2024, 12(12), 2345; https://doi.org/10.3390/jmse12122345 (registering DOI) - 20 Dec 2024

Abstract

Wetlands are dubbed the “kidneys of the earth” and are involved in climate regulation, carbon sequestration, ecological balance preservation, and reducing the surface water pollution. Ongoing economic development has introduced pressing challenges to wetland environments. In this context, extracting coastal wetland information and [...] Read more.

Wetlands are dubbed the “kidneys of the earth” and are involved in climate regulation, carbon sequestration, ecological balance preservation, and reducing the surface water pollution. Ongoing economic development has introduced pressing challenges to wetland environments. In this context, extracting coastal wetland information and monitoring the dynamic changes are essential. Using long-term sequence Sentinel-2 satellite remote sensing images and field observations, this research proposed a Dynamic Bayesian Network classification model framework based on conjugate gradient updates. We compared the wetland feature extraction effects of the Fletcher–Reeves and the Polak–Ribière–Polyak algorithms of the conjugate gradient. Then, remote sensing combined with the FRDBN classification model was used to extract the information pertinent to wetland feature types and changes in wetland areas and analyze alterations in the distribution characteristics of land cover types. The results showed that the FRDBN model achieved high accuracy (above 96%), and kappa coefficients exceeded 0.96. Long-term monitoring revealed that the area of wetlands increased by 0.85 × 104 hm² from 2016 to 2021. Non-aquatic land cover types exhibited pronounced dynamic changes, with the area of change representing 58–69% of the monitored total. Specifically, the transition between salt marsh vegetation and artificial wetlands was relatively obvious. The FRDBN model provides a new method for extracting wetland feature information. Wetland protection, dynamic monitoring, and carbon sink research can provide robust technology support, facilitating investigations into coastal salt marsh carbon sinks and technological advances in carbon sink assessment. Full article

(This article belongs to the Special Issue New Advances in Marine Remote Sensing Applications)

23 pages, 7503 KiB

Open AccessArticle

Circumferential Background Field Temperature Inversion Prediction and Correction Based on Ground-Based Microwave Remote Sensing Data

by Changzhe Wu, Yuxin Zhao, Peng Wu and Xiong Deng

J. Mar. Sci. Eng. 2024, 12(12), 2344; https://doi.org/10.3390/jmse12122344 (registering DOI) - 20 Dec 2024

Abstract

Microwave radiometers are passive remote sensing devices that provide important observational data on the state of the oceanic and terrestrial atmosphere. Temperature retrieval accuracy is crucial for radiometer performance. However, inversions during strong convective weather or seasonal phenomena are short-lived and spatially limited, [...] Read more.

Microwave radiometers are passive remote sensing devices that provide important observational data on the state of the oceanic and terrestrial atmosphere. Temperature retrieval accuracy is crucial for radiometer performance. However, inversions during strong convective weather or seasonal phenomena are short-lived and spatially limited, making it challenging for neural network algorithms trained on historical data to invert accurately, leading to significant errors. This paper proposes a long short-term memory (LSTM) network forecast correction model based on the temperature inversion phenomenon to resolve these large temperature inversion errors. The proposed model leverages the seasonal periodicity of atmospheric temperature profiles in historical data to form a circumferential background field, enabling the prediction of expected background profiles for the forecast day based on temporal and spatial continuity. The atmospheric profiles obtained using the radiometer retrieval are compensated with the forecast temperature inversion vector on the forecast day to obtain the final data. In this study, the accuracy of the forecast correction model was verified utilizing meteorological records for the Taizhou area from 2013 to 2017. Using a hierarchical backpropagation network based on the residual module for comparison, which had a forecast accuracy error of 0.0675 K, the error of our new model was reduced by 34% under the temperature inversion phenomenon. Meanwhile, error fluctuations were reduced by 33% compared with the residual network algorithm, improving the retrieval results’ stability in the temperature inversion state. Our results provide insights to improve radiometer remote sensing accuracy. Full article

(This article belongs to the Section Marine Environmental Science)

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18 pages, 5399 KiB

Open AccessArticle

Numerical Simulation on the Frequency Response of 3-D Reef–Seawater–Seabed Coupling System Under Seismic Excitation

by Liwen Yan, Xingwei Guo, Xunhua Zhang and Jianghao Qi

J. Mar. Sci. Eng. 2024, 12(12), 2343; https://doi.org/10.3390/jmse12122343 - 20 Dec 2024

Abstract

The seismic safety evaluation of artificial reef islands is of great significance for ensuring their long-term stable operation and the safety of residents’ lives. However, due to an insufficient understanding of coral reefs’ basic characteristics, current research on coral reef seismic stability neglects [...] Read more.

The seismic safety evaluation of artificial reef islands is of great significance for ensuring their long-term stable operation and the safety of residents’ lives. However, due to an insufficient understanding of coral reefs’ basic characteristics, current research on coral reef seismic stability neglects the influence of pore water pressure and abnormal reef layers formed during geological evolution. To further study the impact of earthquakes on coral reefs in the South China Sea, this paper takes Meiji Reef as the research object, establishes a 3-D model containing a saturated coral reef–seawater–seabed coupling system, and considers the influence of abnormally high-porosity weathered layers to study the seismic response of the coupling system in the frequency domain. The results show that ignoring the influence of pore water pressure will underestimate the impact of earthquakes on coral reefs. The seismic waves with a frequency of 4.1 Hz in the horizontal direction have a significant impact on the reef, and the side parallel to the direction of wave propagation is more affected, while the side perpendicular to the direction of wave propagation is less affected. The reef flat near the seawater side is less affected by earthquakes, while that on the lagoon side is more affected. Highly porous, weathered layers increase the seismic impact on reef flats. Full article

(This article belongs to the Section Marine Environmental Science)

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18 pages, 5267 KiB

Open AccessArticle

Sea State Parameter Prediction Based on Residual Cross-Attention

by Lei Sun, Jun Wang, Zi-Hao Li, Zi-Lu Jiao and Yu-Xiang Ma

J. Mar. Sci. Eng. 2024, 12(12), 2342; https://doi.org/10.3390/jmse12122342 - 20 Dec 2024

Abstract

The combination of onboard estimation and data-driven methods is widely applied for sea state parameter prediction. However, conventional data-driven approaches often exhibit limited adaptability to this task, resulting in suboptimal prediction performance. To enhance prediction accuracy, this study introduces Cross-Attention mechanisms to optimize [...] Read more.

The combination of onboard estimation and data-driven methods is widely applied for sea state parameter prediction. However, conventional data-driven approaches often exhibit limited adaptability to this task, resulting in suboptimal prediction performance. To enhance prediction accuracy, this study introduces Cross-Attention mechanisms to optimize the task of real-time sea state parameters prediction for maritime operations, innovatively develops a Residual Cross-Attention mechanism, and integrates it into representative networks for sea state parameter prediction. Three benchmark networks were selected, each evaluated under three configurations, without attention, with Cross-Attention, and with Residual Cross-Attention, resulting in a total of nine experimental scenarios for error assessment. The results demonstrate that both Cross-Attention and Residual Cross-Attention reduce prediction error to varying degrees and improve model robustness. Full article

(This article belongs to the Section Ocean Engineering)

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19 pages, 35110 KiB

Open AccessArticle

Data-Independent Acquisition-Based Quantitative Proteomics Analysis of Fertile Red Eggs and Spermatozoa in Hermatypic Coral Galaxea fascicularis: Revealing Key Proteins Related to Gamete Maturation and Fertilization

by Yinyin Zhou, Jingzhao Ke, Lingyu Zheng, Shaoyang Mo, Xiangbo Liu, He Zhao, Wentao Zhu and Xiubao Li

J. Mar. Sci. Eng. 2024, 12(12), 2341; https://doi.org/10.3390/jmse12122341 - 20 Dec 2024

Abstract

Sexually propagated scleractinian corals are in high demand for coral reef restoration. However, for threatened reef-building corals, many of the molecular mechanisms related to their reproduction remain largely unknown, which forms a major bottleneck in the large-scale cultivation of sexually reproducing corals. In [...] Read more.

Sexually propagated scleractinian corals are in high demand for coral reef restoration. However, for threatened reef-building corals, many of the molecular mechanisms related to their reproduction remain largely unknown, which forms a major bottleneck in the large-scale cultivation of sexually reproducing corals. In this study, we analyzed the proteomic signatures of red eggs and spermatozoa from the ecologically significant coral Galaxea fascicularis, using a data-independent acquisition mass spectrometry (DIA-MS) method. A total of 7741 and 7279 proteins from mature red eggs and spermatozoa were identified, respectively. Among these proteins, 596 proteins were spermatozoa-specific and 1056 were egg-specific. Additionally, a total of 4413 differentially abundant proteins (DAPs) were identified, among which 3121 proteins were up-regulated in red eggs and 1292 proteins were up-regulated in spermatozoa. Furthermore, anenrichment analyses showed that DAPs identified in red eggs were mainly involved in the progesterone-mediated oocyte maturation pathway and lectin pathway; and DAPs detected in spermatozoa were mainly involved in the insulin secretion pathway and metabolic pathways for the generation of energy. This result will contribute to the discovery of the intrinsic regulation pathway of gamete maturation and fertilization. Furthermore, at least 57 proteins associated with gamete maturation and reproduction were identified, including the red fluorescent protein (RFP), vitellogenin proteins (VG), the egg protein (EP), the testis-specific serine/threonine-protein kinase family (TSSKs), and the EF-hand Ca²⁺-binding protein family (EFHC1 and EFHC2). Particularly, the third yolk protein EUPHY was reported for the first time in G. fascicularis. In conclusion, this study unveiled groundbreaking molecular insights into coral sexual reproduction, paving the way for more effective conservation and sustainable development of coral reef ecosystems Full article

(This article belongs to the Section Marine Biology)

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18 pages, 15213 KiB

Open AccessArticle

A Feasibility Study of Cross-Medium Direct Acoustic Communication Between Underwater and Airborne Nodes

by Shaojian Yang, Yi Lu, Yan Wei, Jiang Zhu, Xingbin Tu, Yimu Yang and Fengzhong Qu

J. Mar. Sci. Eng. 2024, 12(12), 2340; https://doi.org/10.3390/jmse12122340 - 20 Dec 2024

Abstract

With the rapid advancement of underwater communication and unmanned aerial vehicle (UAV) technologies, the potential applications of cross-medium communication in environmental monitoring, maritime Internet of Things (IoTs), and rescue operations, in particular, have attracted great attention. This study explores the feasibility of achieving [...] Read more.

With the rapid advancement of underwater communication and unmanned aerial vehicle (UAV) technologies, the potential applications of cross-medium communication in environmental monitoring, maritime Internet of Things (IoTs), and rescue operations, in particular, have attracted great attention. This study explores the feasibility of achieving cross-medium direct acoustic communication through the air–water interface. Specifically, it investigates challenges such as acoustic impedance mismatches and signal attenuation caused by energy loss during interface transmission, aiming to understand their impact on communication performance. Experimental tests employed underwater acoustic transducers as signal transmitters to propagate sound waves directly into the air, attempting to establish communication links with aerial UAV nodes. Preliminary experimental results indicate that even conventional underwater acoustic transducers can achieve information exchange between underwater nodes and UAVs, laying a foundation for further research and application of cross-medium communication systems. Full article

(This article belongs to the Section Ocean Engineering)

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27 pages, 29442 KiB

Open AccessArticle

Sinking Particle Fluxes at the Jan Mayen Hydrothermal Vent Field Area from Short-Term Sediment Traps

by Alexey A. Klyuvitkin, Marina D. Kravchishina, Dina P. Starodymova, Anton V. Bulokhov and Alla Yu. Lein

J. Mar. Sci. Eng. 2024, 12(12), 2339; https://doi.org/10.3390/jmse12122339 - 20 Dec 2024

Abstract

The mixing of hydrothermal vent fluids with deep ocean water and near-vent pelagic matter results in particle populations with a complex composition consisting of hydrothermally derived, rock-forming, and biogenic particles. This study is the first investigation of deep sediment trap material collected at [...] Read more.

The mixing of hydrothermal vent fluids with deep ocean water and near-vent pelagic matter results in particle populations with a complex composition consisting of hydrothermally derived, rock-forming, and biogenic particles. This study is the first investigation of deep sediment trap material collected at the Jan Mayen hydrothermal vent field area at 71° N and 6° W of the southernmost Mohns Ridge in the Norwegian–Greenland Sea. This area is characterized by high magmatic activity, axial volcanic ridges, and mafic-hosted volcanogenic massive sulfide deposits. Data on sinking particle fluxes from two hydrothermal settings, the Troll Wall and Soria Moria vent fields, located about 4 km apart, are discussed in the article. In particular, the study emphasize the differences between two hydrothermal settings from each other that demonstrate the geodiversity of hydrothermal processes within the relatively shallow Jan Mayen hydrothermal vent field area affected by the Iceland and Jan Mayen hotspots. The fluxes of sinking hydrothermally derived particles (barite, gypsum, non-crystalline Fe-Si oxyhydroxides, and Fe, Zn, and Cu sulfides) obtained at the Jan Mayen hydrothermal vents made it possible to elucidate the characteristic features of their buoyancy plumes and compare them with similar data reported for other submarine hydrothermal systems. In terms of the composition of the deep-sea hydrothermal particles from buoyant plumes, the studied vent fields are most similar to the Menez Gwen and Lucky Strike vent fields affected by the Azores hotspot. The supply of hydrothermally derived matter is accompanied by normal pelagic/hemipelagic sedimentation, which is dominated by biogenic particles, especially in the upper water layers. Full article

(This article belongs to the Section Geological Oceanography)

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14 pages, 4138 KiB

Open AccessArticle

Use of Spectral Clustering for Identifying Circulation Patterns of the East Korea Warm Current and Its Extension

by Eun Young Lee, Dong Eun Lee, Hye-Ji Kim, Haedo Baek, Young Ho Kim and Young-Gyu Park

J. Mar. Sci. Eng. 2024, 12(12), 2338; https://doi.org/10.3390/jmse12122338 - 20 Dec 2024

Abstract

A graphical clustering approach was used to objectively identify prevalent surface circulation patterns in the East/Japan Sea (EJS). By applying a spectral clustering algorithm, three distinct patterns in the East Korea Warm Current (EKWC) and its extension were identified from daily maps of [...] Read more.

A graphical clustering approach was used to objectively identify prevalent surface circulation patterns in the East/Japan Sea (EJS). By applying a spectral clustering algorithm, three distinct patterns in the East Korea Warm Current (EKWC) and its extension were identified from daily maps of reanalyzed sea surface heights spanning the past 30 years. The results are consistent with previous studies that used manual classification of the EKWC’s Lagrangian trajectories, highlighting the effectiveness of spectral clustering in accurately characterizing the surface circulation states in the EJS. Notably, the recent dominance of northern paths, as opposed to routes along Japan’s coastline or those departing from Korea’s east coast further south, has prompted focused re-clustering of the northern paths according to their waviness. This re-clustering, with additional emphasis on path length, distinctly categorized two patterns: straight paths (SPs) and large meanders (LMs). Notably, SPs have become more prevalent in the most recent years, while LMs have diminished. An autoregression analysis reveals that seasonal anomalies in the cluster frequency in spring tend to persist through to the following autumn. The frequency anomalies in the SPs correlate strongly with the development of pronounced anomalies in the gradient of meridional sea surface height and negative anomalies in the surface wind stress curl in the preceding cold seasons. This relationship explains the observed correlation between a negative Arctic Oscillation during the preceding winter and the increased frequency of SPs in the subsequent spring. The rapid increase in the occurrence of SPs indicates that a reduction in LMs limits the mixing of cold, fresh, northern waters with warm, saline, southern waters, thereby reinforcing the presence of SPs due to a strengthened gradient of meridional surface height and contributing to a slowdown in the regional overturning circulation. Full article

(This article belongs to the Section Physical Oceanography)

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18 pages, 8559 KiB

Open AccessArticle

A Deep Learning Method for Inversing 3D Temperature Fields Using Sea Surface Data in Offshore China and the Northwest Pacific Ocean

by Xiangyu Wu, Mengqi Zhang, Qingchang Wang, Xidong Wang, Jian Chen and Yinghao Qin

J. Mar. Sci. Eng. 2024, 12(12), 2337; https://doi.org/10.3390/jmse12122337 - 20 Dec 2024

Abstract

Three-dimensional ocean temperature field data with high temporal-spatial resolution bears a significant impact on ocean dynamic processes such as mesoscale eddies. In recent years, with the rapid development of remote sensing data, deep learning methods have provided new ideas for the reconstruction of [...] Read more.

Three-dimensional ocean temperature field data with high temporal-spatial resolution bears a significant impact on ocean dynamic processes such as mesoscale eddies. In recent years, with the rapid development of remote sensing data, deep learning methods have provided new ideas for the reconstruction of ocean information. In the present study, based on sea surface data, a deep learning model is constructed using the U-net method to reconstruct the three-dimensional temperature structure of the Northwest Pacific and offshore China. Next, the correlation between surface data and underwater temperature structure is established, achieving the construction of a three-dimensional ocean temperature field based on sea surface height and sea surface temperature. A three-dimensional temperature field for the water layers within the depth of 1700 m in the Northwest Pacific and offshore China is reconstructed, featuring a spatial resolution of 0.25°. Control experiments are conducted to explore the impact of different input variables, labels, and loss functions on the reconstruction results. This study’s results show that the reconstruction accuracy of the model is higher when the input variables are anomalies of sea surface temperature and sea surface height. The reconstruction results using the mean square error (MSE) and mean absolute error (MAE) loss functions are highly similar, indicating that these two loss functions have no significant impact on the results, and only in the upper ocean does the MSE value slightly outperform MAE. Overall, the results show a rather good spatial distribution, with relatively large errors only occurring in areas where the temperature gradient is strong. The reconstruction error remains quite stable over time. Furthermore, an analysis is conducted on the temporal-spatial characteristics of some mesoscale eddies in the inversed temperature field. It is shown that the U-net network can effectively reconstruct the temporal-spatial distribution characteristics of eddies at different times and in different regions, providing a good fit for the eddy conditions in offshore China and the Northwest Pacific. The inversed eddy features are in high agreement with the eddies in the original data. Full article

(This article belongs to the Special Issue Ocean Dynamic Processes and Climate Variability: Insights from Hydrographic Observations and Modeling)

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17 pages, 4805 KiB

Open AccessArticle

Seasonal Variability of Golden Tides (Pylaiella littoralis, Phaeophyceae) and Nutrient Dynamics in a Potentially Eutrophic Intertidal Estuary

by Sara Haro, Ricardo Bermejo, Mark G. Healy, Kay Knöeller, Owen Fenton, Svenja Heesch and Liam Morrison

J. Mar. Sci. Eng. 2024, 12(12), 2336; https://doi.org/10.3390/jmse12122336 - 20 Dec 2024

Abstract

Understanding macroalgal bloom development is crucial for managing eutrophication and protecting estuarine ecosystems. In this study, brown macroalgal blooms (i.e., golden tides) were identified in a potentially eutrophic temperate estuary (NW Ireland). Pylaiella littoralis (Phaeophyceae, Ectocarpales) was monitored at low tide over seven [...] Read more.

Understanding macroalgal bloom development is crucial for managing eutrophication and protecting estuarine ecosystems. In this study, brown macroalgal blooms (i.e., golden tides) were identified in a potentially eutrophic temperate estuary (NW Ireland). Pylaiella littoralis (Phaeophyceae, Ectocarpales) was monitored at low tide over seven sampling occasions between June 2016 and August 2017. In situ biomass, tissue nutrients (nitrogen (N) and phosphorus (P)), and isotopic signature (δ¹⁵N contents) were measured, and relations with environmental drivers were explored. Difference Vegetation Index (NDVI) values from Sentinel-2 satellite imagery were used to assess the spatiotemporal dynamics of P. littoralis biomass (2016–2022). The results indicated that NDVI attributed to golden tides were lowest in 2022, during summer (coinciding with high temperatures and high rainfall) and at the lower shore on the right margin of an entering river. The highest tissue P content was recorded in April 2017, coinciding with in situ biomass peaks (spring–early summer), suggesting elevated P demand. Tissue N content (>2%) and N:P ratios (10–30) indicated occasional P limitation but no N limitation. δ¹⁵N data were very low and it was not possible to identify any primary N source. These findings highlight the importance of nutrient management in mitigating golden tides, addressing eutrophication, and preserving estuarine ecosystems. Full article

(This article belongs to the Section Marine Ecology)

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